Written by James C. Morton Jr., Staff Writer. In a randomized, double- blind placebo- controlled, cross-over study, quercetin significantly reduces uric acid levels (7.88 or 8%) in blood plasma in 4 weeks compared to baseline and placebo group.
Hyperuricemia is one of the most common metabolic disorders that cause gout (1). It is characterized by high concentrations (>6.8mg/dL or >400µmol/L for men and >6.0mg/dL or >360µmol/L for women) of uric acid in blood plasma due to an under-excretion (enhance reabsorption = most patients) or overproduction (exdogenous = diet rich in purines and chronic exposure to fructose or endogenous = increase purine nucleotide breakdown) factors or a combination of both (alcohol consumption = accelerated hepatic breakdown of ATP & organic acid competing with urate for secretion) (2).
Uric acid is produced by the catabolism of deoxyribonucleotides and purine nucleotides with 30% metabolized by intestinal flora and expelled through feces, and 70% metabolized and excreted through the kidneys (3). Hyperuricemia can be asymptomatic with no required treatment, although when urate crystals develop in synovial tissue and around joints, it is termed gout. Latest statistics shows that the estimated healthcare cost for gout in the United States is $7.7 billion annually, with 13% involving rheumatic arthritis (4).
The most popular treatment approach for gout is the use of the prescription medication allopurinol (Zyloprim). It directly prevents the increase of uric acid levels by inhibiting the enzyme xanthine oxidase (oxidoreductase) or xanthine dehydrogenase that processes the final step for producing uric acid (5). Unfortunately, this medication and other chemicals used for this condition can cause serious side effects like stomach pain, bleeding, and jaundice (6).
Fortunately, a 2016 study (7) reveals that quercetin helps lower uric acid levels in blood plasma in pre-hyperuricaemic patients without affecting fasting glucose, urinary excretion of uric acid, and blood pressure. The study involved 22 healthy men aged 19 to 65 with pre-hyperuricaemia. They were given either 500 milligrams a day of quercetin or a placebo for 4 weeks (and then the groups were reversed), with a 4-week washout period between treatments. Before, during, and after the study, uric acid plasma concentration levels were measured and urinary quercetin was also measured (8).
After 4 weeks, researchers noted the following:
| Plasma Uric Acid µmol/l - Measured Time | Quercetin Group - 500mg | Placebo Group |
|---|---|---|
| 2 Weeks | 4.85% Decrease (330 to 314) p-value not significant (0.06) | 3.1% Increase (315 to 325) p-value not significant (0.27) |
| 4 Weeks | 8% (7.88) Decrease (330 to 304) p-value significant (0.008) | 1.6% Increase (315 to 320) p-value not significant (0.60) |
Changes to other measured factors (Plasma glucose, Systolic Blood Pressure, Diastolic Blood Pressure, and Renal excretion) were not significant in both groups. However, the diastolic blood pressure showed a decrease from 73.8 to 71.8 mmHg in 4 weeks with the quercetin group.
When suggesting how quercetin benefits those with pre-hyperuricemia or hyperuricemia, the researchers pointed to quercetin’s strong direct inhibition to xanthine oxidoreductase (9) by having properties of flavonoids and antioxidants to reduce uric acid and prevent crystallization (gout) (10). They further concluded that quercetin has shown potential to decrease hypertension in population studies (11, 12, 13), and that quercetin should be evaluated in populations with lower plasma uric acid, female hypertension individuals, and older and younger populations. Researchers noted limitations related to few studies conducted, no assessment of habitual diet (100g of fresh red onion = 500mg of quercetin aglycone), and stated there were no adverse events.
Source: Shi Y, Williamson G. Quercetin lowers plasma uric acid in pre-hyperuricaemic males: a randomized, double-blinded, placebo-controlled, cross-over trial. British Journal of Nutrition 2016 Mar:20 (115):5:800-806. doi:10.1017/S0007 114515005310. Epub 2016 Jan 20.
© The Authors 2016
Posted March 14, 2016.
References:
- “Hyperuricemia” posted on the Medscape website.
- “Hyperuricemia and Gout” posted on the Center for Disease Control and Prevention website.
- Grassi D, Ferri L, Desideri G, Giosia P, Cheli P, Pinto R, Properzi G, Ferri C. 2013. Chronic Hyperuricemia, Uric Acid Deposit and Cardiovascular Risk. Curr Pharm Des. 19:(13), 2432-2438.
- ”Gout Statistic” posted on the Center for Disease Control and Prevention website.
- Becker MA, Schumacher HR Jr, Wortmann RL, et al. (2005) Febuxostat compared with allopurinol in patients with hyperuricemia and gout. N Engl J Med 353, 2450–2461.
- “Gout and Hyperuricemia” posted on WebMD website.
- Shi Y, Williamson G. Quercetin lowers plasma uric acid in pre-hyperuricaemic males: a randomized, double-blinded, placedbo-controlled, cross-over trial. British Journal of Nutrition 2016 Mar:20 (115):5:800-806. doi:10.1017/S0007 114515005310. Epub 2016 Jan 20.
- Shi Y & Williamson G (2015) Comparison of the urinaryexcretion of quercetin glycosides from red onion and aglycone from dietary supplements in healthy subjects: a randomized, single-blinded, cross-over study. Food Funct 6,1443–1448.
- Day AJ, Bao Y, Morgan MR, et al. (2000) Conjugation position of quercetin glucuronides and effect on biological activity.Free Radic Biol Med 29, 1234–1243.
- Cook NR, Cohen J, Hebert PR, et al. (1995) Implications of small reductions in diastolic blood pressure for primary prevention. Arch Intern Med 155, 701–709.
- Whelton PK, He J, Appel LJ, et al. (2002) Primary prevention of hypertension: clinical and public health advisory from The National High Blood Pressure Education Program. JAMA 288,1882–1888.
- Edwards RL, Lyon T, Litwin SE, et al. (2007) Quercetin reduces blood pressure in hypertensive subjects. J Nutr 137, 2405–2411.
- Pfeuffer M, Auinger A, Bley U, et al. (2013) Effect of quercetin on traits of the metabolic syndrome, endothelial function and inflammation in men with different APOE isoforms. Nutr Metab Cardiovasc Dis 23, 403–409.
